Method for manufacturing glass clichéusing laser etching and apparatus for laser irradiation therefor

ABSTRACT

A method for manufacturing a glass cliché using laser etching includes a dipping step for dipping a glass cliché, which will be etched, into an etching solution, a patterning step for irradiating laser to the glass cliché dipped in the etching solution to form a pattern therein, and a washing step for washing the patterned glass cliché. This method allows making a cliché with a high aspect ratio and fine line widths in comparison to a conventional cliché manufacturing method using photoresist for etching, and also ensures more efficient energy consumption and higher etching efficiency rather than an etching method using laser only.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a glasscliché using laser etching and an apparatus for laser irradiationtherefor, and more particularly to a method for manufacturing a glasscliché using the phenomenon that an etching speed of glass is relativelyincreased only in a portion to which laser is irradiated.

2. Description of the Related Art

To produce a flat panel display (FPD) such as a liquid crystal display(LCD) and a plasma display panel (PDP), various kinds of patterningprocesses for making electrodes, black matrix, color filters,separators, thin film transistors and so on are required.

In a general case, a photoresist is selectively removed using a photomask by exposing and developing to make a photoresist pattern, and thenthe photoresist pattern is used for the patterning process. Thispatterning process using a photo mask uses a lot of materials such asphotoresist and developing agent and also needs an expensive photo mask,which results in many processing steps or long processing time.

To solve this problem, there have been proposed various methods forprinting a pattern-forming material directly such as ink jet printing orlaser transcription, without using photoresist. As one of such methods,there is an offset printing in which a patterned material is transcribedto a blanket using a cliché and then the pattern of the blanket istranscribed onto a cliché.

The offset printing using a cliché ensures smaller material consumptionand simpler process than a conventional method using photoresist andalso ensures faster process speed than ink-jet printing or lasertranscription. However, the offset printing needs clichés independentlyfor substrates with different patterns, and a cliché generally made ofglass is manufactured complicatedly and very expensive.

A general method for making the glass cliché is explained with referenceto FIG. 1. A photoresist 102 is applied onto a glass cliché 101 by meansof spin coating, dip coating, spray coating, slit coating, bar coatingor the like, as shown in FIG. 1( a).

After that, a photo mask 103 is used to form a desired pattern as shownin FIG. 1( b) by means of exposure and development phenomena. During theexposure process, the photoresist 102 is selectively photo-sensitized byUV rays 104 passing through the photo mask 103 in which a desiredpattern is already formed, and a pattern 105 is formed on the glasscliché as shown in FIG. 1( c) due to the difference of solubility for adeveloping solution between the photo-sensitized region and thenon-sensitized region.

FIG. 1( c) shows the case adopting a positive photoresist, but anegative photoresist may also be used. In case the negative photoresistis used, a region irradiated by UV rays 104 remains but a region notphoto-sensitized by UV rays is removed.

The glass cliché having the pattern of the photoresist 102 formedtherein is dipped in a glass etching solution (not shown) as shown inFIG. 1( d), and then glass etching reaction occurs partially only on aregion 106 where a glass cliché is exposed. Generally, an etchingreaction of an amorphous material such as glass becomes an isotropicetching without no orientation, so an etching speed is identical in bothdepth and width directions of the glass.

Thus, as the etching reaction occurs, a glass etching region 106 becomeswider than the width of the pattern of the photoresist 102, and a bottomportion of the etching portion has a rounded shape, as shown in FIG. 1(d). As the etching work progresses, the etching continuously occurs indepth and width directions as shown in FIG. 1( e), so a width 107 of theetched glass cliché becomes gradually wider than the pattern of thephotoresist 102.

If the etching is completed to a desired depth, the glass cliché istaken out of the etching solution and washed by a distilled water, andthen the photoresist is removed to obtain a glass cliché 108 finallyetched, as shown in FIG. 1( f).

In the method of making a glass cliché using such a wet etching,isotropic etching occurs as shown in FIG. 1, so the pattern is etched inits sides as much as the same thickness as the etched depth.

Thus, the pattern of photoresist used for etching should be formed withat least double margin of a desired etching depth, and due to thisreason, there is a limit in precision for the pattern to be formed.Also, considering a room where an etching solution may penetrate, anactually etchable pattern should be three or four times as much as aminimal etching depth, so it is more difficult to form a pattern withfine line widths.

In addition, due to the nature of isotropic etching, the etching is madein a substantially circular shape between a wall and a bottom to beetched, so an etching depth is gradually varying, which results indeteriorated printing quality. Also, since a photoresist pattern shouldbe formed prior to the etching process, many processes such as anexposure process using a photo mask and a photoresist developmentprocess using a developing solution are needed before the etching work,and also a process of removing the remaining photoresist is also addedafter the etching work is completed.

In addition to the above wet etching, a dry etching for etching a glassusing plasma of an etching gas in a vacuum state is also available. Thedry etching for etching a glass cliché using a gas containing fluorinesuch as CF4 and CF3H allows anisotropic etching, differently from thewet etching, so a line width is not widened or a region between a walland a bottom is not etched in a circular shape as the dry etchingprogresses.

However, a vacuum chamber and an expensive etching gas should beprepared for the dry etching, which increase a cost for the etching workand makes it difficult to apply the etching work to large-scale mattersor mass production.

Also, the drying etching makes an etching mask and an etching materialbe etched together, so the etching mask should have as slowest etchingspeed as possible. Generally, a mask layer made of metal such as chromeis used for glass etching, but this mask layer cannot be made too thick,so there is a limit in glass etching depth.

In addition, the dry etching needs to form a mask pattern prior toetching, similarly to the wet etching, so many processes such aspreprocesses for vacuum-deposition of a metal mask layer, formation of aphotoresist layer, exposure of the photoresist using a photo mask,development of the photoresist layer to form a pattern, etching of themetal layer used as a mask as well as postprocesses for removal of themetal mask after etching are required.

In order to solve the above problems in a glass cliche making processusing wet etching or dry etching, a new method using laser etching isproposed in the Korean Laid-open Patent Publication No. 10-2007-0000100or the like.

The Korean Laid-open Patent Publication No. 10-2007-0000100 discloses amethod for making a cliché having a desired pattern by directly etchingan insulating substrate with laser. In case a glass cliché is directlyetched with laser to make a cliché, there may be advantages in processsince an etching solution is not used. However, since the glass isremoved by means of photothermolysis on regions irradiated by laser, theused laser should have a high power and an etching speed is relativelyslow. Also, it is impossible to prevent generation of HAZ (Heat AffectedZone) that may cause pattern deterioration, and fine cracks may happenin the glass cliché due to thermal impacts caused by continuousirradiation of the laser with strong energy.

Along with them, since a roll means playing a role of moving a materialtranscribed to a glass cliché continuously transfers load to the glasscliché, the load may weaken durability of the glass cliché or causesfine cracks in the glass cliché. Also, residuals of pattern material,not moved by the roll means, may remain in a blanket.

SUMMARY OF THE INVENTION

The present invention is designed to solve the problems of the priorart, and therefore it is an object of the present invention to provide amethod for etching a glass cliché with a high aspect ratio and high workefficiency by means of harmonized use of wet etching and laser etching.

In addition, another object of the present invention is to provide amethod for etching a glass cliché, which may effectively disperse aphysical load of a roll means, transferred to a glass cliché, anddifferentially control a laser irradiation area according to anirradiation time such that a pattern capable of minimizing residuals ofa blanket may be formed on the glass cliché.

Other objects and advantages of the present invention will be explainedbelow and understood from embodiments of the present invention. Inaddition, the objects and advantages of the present invention may berealized by combinations of components defined in the appended claims.

In order to accomplish the above object, the present invention providesa method for manufacturing a glass cliché using laser etching,comprising a dipping step for dipping a glass cliché, which will beetched, into an etching solution; a patterning step for irradiatinglaser to the glass cliche dipped in the etching solution to form apattern therein; and a washing step for washing the patterned glasscliché.

Also, in the patterning step, a pattern may be formed by means of aplurality of laser irradiation surfaces applied to the glass cliché. Inaddition, the pattern formed by the plurality of irradiation surfaces ispreferably made using a mask having a laser transmission patternidentical to the pattern to be formed on the glass cliché.

In the present invention, the patterning step includes an input step forreceiving image information of a pattern to be formed; an calculatingstep for calculating area information of a laser irradiation surfacecorresponding to the image information; and an irradiating step forirradiating laser having differential irradiation areas according toirradiation time based on the calculation area information to form apattern.

In addition, in the irradiating step, a pattern is preferably formed byirradiating laser whose irradiation area is decreased as the irradiationtime goes.

In another aspect of the present invention, there is also provided anapparatus for laser irradiation, which is used for laser etching to forma pattern on a glass cliché dipped in an etching solution by irradiatinglaser thereto, the apparatus comprising a laser source for irradiatinglaser; an input unit for receiving shape information of the pattern tobe formed; an calculation unit for calculating area information of alaser irradiation surface corresponding to the shape information; and acontroller for controlling the laser source to irradiate laser havingdifferential irradiation areas according to irradiation time based onthe calculated area information.

In the apparatus for laser irradiation, the controller preferablycontrols the laser source to irradiate laser whose irradiation area isdecreased as the irradiation time goes.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the present invention will become apparentfrom the following description of embodiments with reference to theaccompanying drawing in which:

FIG. 1 is a flowchart illustrating a conventional method formanufacturing a general glass cliché;

FIG. 2 is a flowchart illustrating a method for manufacturing a glasscliché according to one embodiment of the present invention;

FIG. 3 is a block diagram showing a laser irradiation apparatus forlaser etching according to one embodiment of the present invention;

FIG. 4 is a flowchart illustrating a laser etching process according toan embodiment of the present invention;

FIG. 5 is a schematic view showing a laser etching process according toanother embodiment of the present invention;

FIG. 6 is a schematic view showing a printing process using an organiccliché;

FIG. 7 shows a differential irradiation method based on laserirradiation areas according to a preferred embodiment of the presentinvention; and

FIG. 8 shows a differential irradiation method based on laserirradiation areas according to another embodiment of the presentinvention.

<Reference Numeral of Essential Parts in the Drawings> 300: laserirradiation apparatus 302: input unit 304: calculation unit 306:controller 308: laser source 401: glass cliché 402: irradiated laser403: blanket 405: mirror 410: shadow mask

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentinvention on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation.

Therefore, the description proposed herein is just a preferable examplefor the purpose of illustrations only, not intended to limit the scopeof the invention, so it should be understood that other equivalents andmodifications could be made thereto without departing from the spiritand scope of the invention.

Referring to FIG. 2 that is a flowchart illustrating processes of amethod for manufacturing a glass cliché according to a preferredembodiment of the present invention, the glass cliché manufacturingmethod of the present invention includes a dipping step (S200) fordipping a glass cliché, which will be etched, into an etching solution,a patterning step (S210) for irradiating laser to the glass clichédipped in the etching solution to form a pattern therein, and a washingstep (S220) for washing the patterned glass cliché.

First, a glass cliché, which will be etched, is dipped in an etchingsolution used for wet etching (S200). The etching solution in which theglass cliché is dipped may use at least one solution selected fromcompounds containing hydrofluoric acid, ammonium fluoride or BOE(buffered oxide etch) solution.

In case the glass cliché is dipped in the etching solution, the glasscliché is preferably fixed to a position fixing means to keep itshorizontal and vertical balance so as to ensure straightness of laserirradiation and keep precision of patterning.

Using the glass cliché dipped in the etching solution as a subject forirradiation, a predetermined desired pattern is formed therein (S210). Alaser moving trajectory corresponding to the predetermined desiredpattern may be input in advance and then used for driving the lasersource such that a desired pattern may be formed automatically.

The region irradiated by laser as mentioned above partially bringsimprovement of an etching speed thermochemically or optochemically,thereby locally increasing an etching speed. Also, since the etchingprogresses only in a direction irradiated by laser, a configurationcapable of forming an etching pattern with a great aspect ratio may berealized.

Etching occurs in a region irradiated by laser, so a distance from alaser irradiation apparatus to a cliché surface is preferably controlledsuch that a focus may be formed at the glass surface. Also, in case adepth to be etched is greater than a depth of focus of laser, it ispreferred that the position of a lens is controlled according to anetched depth as the etching work progresses.

In addition, in order to sufficiently improve an optochemical orthermochemical etching speed by laser, it is required to use awavelength absorbed by a glass to be etched, but glasses generally haveno absorption in a visible ray or UV ray region, so it is advantageousto use fourth harmonics of Nd:YAG laser or use a laser having awavelength in UV region such as KrF laser or ArF laser for etching.Also, if the intensity of radiation is sufficient at a focus portion oflaser, multiphoton absorption occurs to generate optochemical orthermochemical etching, so using a laser with a wavelength in UV regionis not essential.

As an example, UV rays in 355 nm wavelength, which is third harmonics ofNd:YAG laser are not absorbed in a glass cliché, but multiphotonabsorption occurs when using a pulse laser in Q switching manner withhigh pulse energy, which allows dry etching or wet etching of a glasscliché.

After the laser irradiating step is performed as mentioned above, theglass clichéis washed using water or distilled water (S220).

The laser etching method mentioned above is not explained below in moredetail with reference to FIG. 4.

Laser 402 is irradiated to a glass cliché 401 as shown in FIG. 4( a).Though not shown in the figure, the glass cliché shown in FIG. 4( a) ispresumed as being dipped in an etching solution.

If the laser 402 is irradiated, etching occurs in an irradiated regionalong an irradiation direction (namely, in a vertical direction),thereby forming a blanket 403 as shown in FIG. 4( b). The processesexplained above based on FIGS. 4( a) and 4(b) are repeatedly applied toanother point of the glass cliché to form a different pattern (see FIGS.4( c) and 4(d)), and as a result a glass cliché 401 having the blanket403 as shown in FIG. 4( e) is manufactured.

Also, in the present invention, the patterning step S210 is preferablyexecuted such that a pattern is formed by means of a plurality of laserirradiation surfaces irradiated to the glass cliché. Namely, in case aplurality of patterns are formed, using only one laser requires a lot ofworking time as much. Also, speed or progress of etching reaction by anetching solution may be varied between a pattern formed former and apattern formed later, so it is more preferred that a plurality ofirradiation surfaces are formed to ensure precise formation of manypatterns.

In order to form a plurality of laser irradiation surfaces, variousmethods may be used. For example, a plurality of laser sources may beused, and light emitted from one laser or a plurality of lasers may besplit using several partially transmitting mirrors. Also, an opticaldiffraction device may be used to split light one or several laserlights into more lights, and a polygon mirror rotating at a high speedmay also be used to split light. In addition, a digital mirror devicemay also be used to expose a certain area to light. Such methods may beapplied depending on implementation patterns or work conditions.

Moreover, in order to form a plurality of irradiation surfaces, as shownin FIG. 5, a shadow mask may be used (FIG. 5( a)), and a scanning methodmay also be used (FIG. 5( b)).

As shown in FIG. 5, the laser covering a wide area at once is preferablyirradiated to a mask having a laser transmission pattern identical tothe pattern to be formed on the glass cliché such that a desired patternis formed at the same time. Since the laser is transmitted through thepattern formed in the mask, a laser having a plurality of irradiationareas may be irradiated in a desired pattern on the glass cliché.

In case a shadow mask is used, laser is irradiated over a wide area atonce, so a laser with high energy such as excimer laser is usedadvantageously. This kind of laser may etch a wide area within a shorttime and facilitate processing a pattern with various line widths. Thislaser may adopt excimer laser such as KrF laser and ArF laser.

Along with it, as shown in FIG. 5( b), a scanner is used for moving alaser beam 402 concentrated on a focus to a desired position by usingtwo independently driven mirrors 405 such that the laser beam 402 ismoved into a desired shape and thus forms a blanket 403 on the glasscliché 401 at an accelerated etching speed.

In case etching is conducted using a laser beam concentrated on a focusin a scanning manner, this etching method may be applied directly tovarious kinds of patterns, and particularly it is effective in forming aline-shaped pattern. The laser processing using the scanner manner mayadopt CO₂ laser, Nd:YAG laser, He—Cd laser or the like.

Hereinafter, a configuration having a time-functional laser irradiationarea or width for accomplish another object of the present invention isexplained in detail.

To achieve another object, the patterning step (S210) of the presentinvention preferably includes an input step (S212) for receiving shapeinformation of a pattern to be formed, a calculating step (S214) forcalculating area information of a laser irradiation surfacecorresponding to the image information, and an irradiating step (S216)for irradiating laser having differential irradiation areas according toirradiation time based on the calculation area information to form apattern. Also, a laser irradiation apparatus 300 for realizing the abovemethod includes an input unit 302, a calculation unit 304, a controller306 and a laser source 308.

As shown in FIG. 6, in the offset printing method, as a predeterminedroll means 500 rotates, a pattern material 404 transcribed to a blanket403 of a glass cliché 401 is moved to the roll means 500 as a patternidentical to the pattern of the glass cliché, and as a following work,the pattern of the roll means is transcribed again to a predeterminedcliché that needs transcription.

During the above procedure, the roll means 500 continuously applies aphysical load to the glass cliché 401, which may case a crack in theglass cliché. Also, in case the pattern material 404 transcribed to theblanket 403 of the glass cliché 401 is moved to the roll means 500, atangential direction of the roll means may be considered as beingcoincided with a horizontal direction of the blanket when the roll meansis in contact with the blanket. However, since the roll means makesrotation, both directions are not coincided before or after the contactperiod.

Due to such a physical movement, printing materials not moved to theroll means remain in the blanket, for example in a lower side of theblanket.

For an effective solution to the above problem, the pattern formed onthe glass cliché is preferably wider in its lower portion than in itsupper portion so as to distribute force and improve easy movement of thepattern material. The shape of the pattern may also be modified invarious ways, including a trapezoidal shape with a longer base,according to work environments, pattern material, features of the rollmeans, physical characteristics of the glass cliché, or the like.

The input unit 302 of the laser irradiation apparatus 300 of the presentinvention for realizing the above configuration firstly receives shapeinformation of a pattern, which will be formed, in case laser isirradiated to a glass cliché (S212). Various information such as shapefeatures of the pattern, an aspect ratio, a ratio of top and bottom of apattern depth, a linear feature of a terminal end, and so on are input.

After that, the calculation unit 304 calculates an actual irradiationarea or a width of irradiated laser beam according to a time function inconsideration of the input shape information, intensity and wavelengthof laser source, power supply environments and so on as variables suchthat the irradiated laser may correspond to the shape of the pattern(S214).

Namely, as shown in FIGS. 7( a) and 8(a) illustrating a laserirradiation area function using time (t) as an x axis and an irradiationarea (s) as a y axis, the calculation unit 304 calculates an irradiationarea value according to time during which laser should be irradiated.

As the controller 306 of the present invention controls the laser source308 to irradiate a laser corresponding to the calculated result, a laserhaving differential irradiation areas according to irradiation timebased on the calculated area information is irradiated to form a desiredpattern (S216).

As a laser whose irradiation area is decreased as the irradiation timegoes is irradiated to form a pattern as mentioned above, the physicalforce applied from the roll means 500 to the glass cliché is effectivelydispersed, which facilitates effectively prevention of any crack in theglass cliché and improves durability of the glass cliché. Also, it ispossible to move the pattern material to the roll means in an easierway, and also it is possible not to remain any residue of patternmaterial in the glass cliché.

The components of the laser irradiation apparatus 300 as mentioned aboveshould be considered not as physically distinguishable components but aslogically distinguishable components. Namely, each component iscorresponding to a logic element realized by an electric or electroniccircuit configurable to realize the spirit of the present invention.Thus, though some components are integrally operated or any component isseparately operated, they should be considered as being included in thescope of the present invention if they may realize the function executedby the logic components of the present invention.

The present invention has been described in detail. However, it shouldbe understood that the detailed description and specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the invention will become apparent to those skilledin the art from this detailed description.

APPLICABILITY TO THE INDUSTRY

According to the present invention, there is no need to use aphotoresist or a photo mask on a glass cliché in advance, so it ispossible to manufacture a glass cliché with simple processes at a lowcost.

Also, since the improved features of the wet etching against a laserirradiation surfaces are used, it is possible to easily form a patternwith a great aspect ratio and fine line widths. In addition, effectiveetching is ensured even with a laser source having small energy, so thepresent invention may provide a more economic glass clichémanufacturingmethod.

Further, since differential etching according to irradiation time isconducted to form a patter on a glass cliché, it is possible to form apattern structure capable of effectively dispersing a physical force ofa roll means, transferred to the glass cliché. Also, using the abovestructure, it is possible to minimize any residue of pattern material.

1-7. (canceled)
 8. An apparatus for laser irradiation, which is used forlaser etching to form a pattern on a glass cliché dipped in an etchingsolution by irradiating laser thereto, the apparatus comprising: a lasersource for irradiating laser; an input unit for receiving shapeinformation of the pattern to be formed; an calculation unit forcalculating area information of a laser irradiation surfacecorresponding to the shape information; and a controller for controllingthe laser source to irradiate laser having differential irradiationareas according to irradiation time based on the calculated areainformation.
 9. The apparatus for laser irradiation according to claim1, wherein the controller controls the laser source to irradiate laserwhose irradiation area is decreased as the irradiation time goes.